A Note on the Stability of a Valve Amplifier

This paper considers the stability of a valve amplifier which has an oscillatory circuit in the grid and in the anode circuit. An exact condition for stability is obtained for circuits which have no resistance, and it is shown that when both circuits have the same natural frequency instability is then impossible if the anode inductance exceeds μ times the grid circuit inductance. This condition is believed to be new; in practice it is unnecessarily severe, but it is believed that stability should be sought by increasing the anode inductance and the grid circuit capacity. The stability of circuits which have resistance is too cumbersome to express generally, but it is discussed on broad principles; the stability and amplification of multistage amplifiers are also considered briefly. The following papers should be compared with the present one.

I. A record of experiments upon the functions of the cerebral cortex

The paper consists, as its title implies, of a record of experiments relating to the functions of the cerebral cortex, a subject upon which the authors have been engaged during three years. The experiments have been entirely made upon monkeys. After describing the methods employed, the general results of excitation and of extirpation of various parts of the cerebral hemispheres on one or both sides are given, and the cases in which the method of ablation has been employed are then recorded in detail, the symptoms observed during life and the condition of the brain after death being systematically noted. Each case is illustrated by one or more drawings, showing the exact condition of the brain post mortem . In some instances sections of the brain are also represented. The paper includes also a topographical plan of the excitable or motor region of the cortex cerebri .